Over-voltage protection device for resonant wireless power transmission device and method for controlling the over-voltage protection device

ABSTRACT

A wireless power transmission device is provided. The wireless power transmission device includes a resonance signal generator and a controller. The resonance signal generator is configured to transmit wireless power to a wireless power reception device. The controller is configured to adjust the wireless power transmitted to the wireless power reception device, when a predetermined condition caused by over-voltage protection operation at the wireless power reception device is detected.

PRIORITY

This application is a Continuation Application of U.S. patentapplication Ser. No. 13/722,211 and claims priority under 35 U.S.C.§119(a) to a Korean Patent Application filed in the Korean IntellectualProperty Office on Jan. 11, 2012, and assigned Serial No.10-2012-0003341, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a wireless power transmissionand reception technique applied to a wireless charging technique, andmore particularly, to an over-voltage protection device for atransmission device in a resonant wireless power transmission andreception technique and a method for controlling the over-voltageprotection device.

2. Description of the Related Art

A wireless charging (or non-contact charging) technique using wirelesspower transmission and reception has recently been developed and usedfor various electronic devices. The wireless charging technique allows auser to automatically charge a battery by simply placing it on acharging deck without connecting a device such as a cellular phone, to aseparate charging connector.

Wireless electric toothbrushes and wireless electric shavers arecommonly known devices that use the wireless charging technique. Thewireless power transmission and reception technique may increase sealingforce and waterproof features as it wirelessly charges electronicproducts and thus does not need an external charging terminal, and mayalso increase portability of electronic devices because it does notrequire wired chargers. The wireless charging related technique isexpected to evolve significantly in the growing era of electricvehicles.

The wireless charging technique roughly includes an electromagneticinduction scheme using coils, a resonant scheme using resonance, and aRadio Frequency (RF)/microwave radiation scheme that converts electricalenergy into a microwave and transfers the energy. An electromagneticinduction-based power transmission method involves transferring powerbetween a primary coil and a secondary coil. The resonant scheme usesfrequency resonance between a transmission device and a reception devicethat use a resonance frequency.

In the wireless power transmission and reception technique, whenabnormal conditions occur, such as incorrect placement of a receptiondevice on a charging deck of a transmission device, the reception deviceis abnormal, or a metallic substance is placed on the charging deck,excessive power beyond a normal value may be generated in the receptiondevice. Therefore, a wireless power transmission and reception system aswell as the reception device essentially require an over-voltageprotection circuit.

For the over-voltage protection circuit, a Zener diode may be includedin the reception device. However, the Zener diode needs a preparationperiod corresponding to a time necessary for its operation, and in thatpreparation period, over-voltage protection is difficult to achieve.Moreover, as the amount of power to be handled increases, the size andcapacity of the required Zener diode also increases. In this case, theremay be significant restrictions on a mounting size.

Such restrictions make it difficult to include a corresponding wirelesspower reception device in a portion of an electronic device for which asize limitation is vital. As such, there is a need in the art for anover-voltage protection circuit capable of achieving rapid handling andhaving high efficiency while reducing a mounting size in wireless powertransmission and reception devices.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a resonant wireless powertransmission device, which achieves rapid handling, has high efficiency,easily handles a high over-voltage, and solves a mounting size problem.

According to an aspect of the present invention, a wireless powertransmission device is provided. The wireless power transmission deviceincludes a resonance signal generator and a controller. The resonancesignal generator is configured to transmit wireless power to a wirelesspower reception device. The controller is configured to adjust thewireless power transmitted to the wireless power reception device, whena predetermined condition caused by over-voltage protection operation atthe wireless power reception device is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of an embodiment of thepresent invention will be more apparent from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a resonant wireless power transmission and receptionsystem according to an embodiment of the present invention;

FIG. 2 illustrates a reception device of FIG. 1;

FIG. 3A illustrates over-voltage protection of a controller of areception device of FIG. 1;

FIG. 3B illustrates over-voltage protection of a controller of atransmission device of FIG. 1;

FIG. 4 illustrates a voltage waveform applied to a constant-voltagegenerator of a reception device of FIG. 2;

FIGS. 5A through 5C illustrate voltage waveforms applied to aconstant-voltage generator for respective set capacities of respectivedetuning capacitors included in an over-voltage protector of a receptiondevice of FIG. 2;

FIG. 6 illustrates a rate of power transferred from a transmissiondevice to a reception device with respect to a set capacity of eachdetuning capacitor included in an over-voltage protector of atransmission device of FIG. 2; and

FIGS. 7A through 7F illustrate a rate of power transferred from atransmission device to a reception device with respect to a set capacityof each detuning capacitor included in an over-voltage protector of areception device of FIG. 2.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. In the followingdescription, the same or similar elements may be designated by the samereference numerals in different drawings. Further, detailed descriptionsof known functions and configurations incorporated herein may be omittedfor the sake of clarity and conciseness.

FIG. 1 illustrates a resonant wireless power transmission and receptionsystem according to an embodiment of the present invention, and FIG. 2illustrates a reception device of FIG. 1. Referring to FIGS. 1 and 2,the resonant wireless power transmission and reception system includes awireless power transmission device 1, such as a charging device, and awireless power reception device 2, such as one provided in a portableterminal.

The wireless power transmission device 1 may include a signal generator10 which includes a Voltage Control Oscillator (VCO), to generate asignal of a preset frequency such as a 6.78 MHz resonance frequency; anamplifier 12 which includes an amplification unit that amplifies thesignal generated by the signal generator 10 to a high-power signal; aresonance signal generator 14 which includes a resonator that generatesa wireless resonance signal, for example, of 6.78 MHz according to thehigh-power signal generated by the amplifier 12; a voltage/currentdetector 16 that senses (a peak level of) voltage and current of thewireless resonance signal generated by the resonance signal generator14; and a controller 18 that collectively controls a wireless powertransmission operation of the wireless power transmission device 1, andcontrols operations of the signal generator 10 and the amplifier 12 tomaintain a value in a normal range by monitoring a current and a voltageof a wirelessly transmitted resonance signal based on the current andvoltage detected by the voltage/current detector 16.

The wireless power transmission device 1 may further include a sensor 17which includes an object sensor that provides a sensing signal to thecontroller 18 by sensing placement of the wireless power receptiondevice 2, and a wireless communication unit 19 configured to use oneselected from among various wireless near-field communication schemesfor communication with the wireless power reception device 2 in relationto the wireless power transmission operation under control of thecontroller 18.

The controller 18 of the wireless power transmission device 1 mayinclude a Micro Control Unit (MCU) (not shown), and may be configured tomonitor a value detected by the voltage/current detector 16 through anAnalog/Digital Conversion (ADC) port (not shown). In particular, thecontroller 18 determines a periodic impedance change, which is inducedby an over-voltage protection circuit of the wireless power receptiondevice 2 and is detected by the voltage/current detector 16 for anover-voltage protection operation, and adjusts a power supply level ofthe wireless power transmission device 1. The over-voltage protectionoperation of the controller 18 of the wireless power transmission device1 according to the present invention will be described later in detailwith reference to FIG. 3B.

The wireless power reception device 2 may include a resonance signalreceiver 24 which includes a resonator, to receive a wireless resonancesignal transmitted from the resonance signal generator 14 of thewireless power transmission device 1, a rectifier 22 that rectifiesAlternating Current (AC) power received in the resonance signal receiver24 into Direct Current (DC) power, a smoother 21 that smoothes the DCpower rectified by the rectifier 22, a constant-voltage generator 20that converts the power output from the smoother 21 into operating power(e.g., +5V) desired by the portable terminal to which the wireless powerreception device is applied, an over-voltage protector 25 which isdriven by a driver 27 to detune a resonance frequency of the resonatorof the resonance signal receiver 24 during an over-voltage protectionoperation, thereby reducing reception power, a voltage detector 26 thatdetects an input voltage of the constant-voltage generator 20, and acontroller 28 which is implemented with an MCU or the like forcollectively controlling a wireless power reception operation of thewireless power reception device 2, determining whether an over-voltageoccurs according to the signal detected by the voltage detector 26, andoutputting a control signal for driving the over-voltage protector 25 tothe driver 27 for the over-voltage protection operation if determiningthat the over-voltage occurs.

The wireless power reception device 2 may further include a wirelesscommunication unit 29 which uses one selected from among variouswireless near-field communication schemes to communicate with thewireless power transmission device 1 in relation to the wireless powerreception operation under control of the controller 28, and a waveformstabilizer (not shown) which includes an LC circuit to stabilize andoutput a DC waveform output from the constant-voltage generator 20.

Referring to FIG. 2, the rectifier 22 may have a full-bridge diodestructure using four diodes D1, D2, D3, and D4, in which for example, aserial connection circuit of the first and second diodes D1 and D2 and aserial connection circuit of the third and fourth diodes D3 and D4 areconnected in parallel, and out of two nodes connected in parallel, aconnection node of the first and third diodes D1 and D3 is set to be anoutput node of a DC power Input Voltage signal (VIN), and a connectionnode of the second and fourth diodes D2 and D4 is connected with aground terminal.

A terminal VIN_P out of two connection terminals VIN_P and VIN_N of theresonator of the resonance signal receiver 24 is connected with aconnection point of the first and second diodes D1 and D2, and the otherterminal VIN_N is connected with a connection point of the third andfourth diodes D3 and D4.

The smoother 21 may include at least one of parallel-connectedcapacitors C3 and C4.

The constant-voltage generator 20 is provided with the output of therectifier 30 through the smoother 21 and converts the rectified DC powerinto the DC power of a desired level. To this end, the constant-voltagegenerator 20 may include a step-down converter such as a DC-DC buckconverter including a Low Drop Output (LDO).

The over-voltage protector 25 may include resonance-detuning first andsecond capacitors C1 and C2 having ends that are connected to the twoconnection terminals VIN_P and VIN_N of the resonator of the resonancesignal receiver 24, respectively.

The driver 27 may have a switch structure in which the driver 27performs a switching operation according to a control signal output fromthe controller 28 to connect the other terminals (C_OVP1, C_OVP2) of thefirst and second capacitors C1 and C2 of the over-voltage protector 25to the ground terminal.

The controller 28 in a normal state controls a switching state of thedriver 27 to be an open state, such that the other terminals (C_OVP1,C_OVP2) of the first and second capacitors C1 and C2 of the over-voltageprotector 25 maintain the open state. In this case, the first and secondcapacitors C1 and C2 of the over-voltage protector 25 do not affect theresonator of the resonance signal receiver 24. In the over-voltageprotection operation, the controller 28 controls the switching state ofthe driver 27 to be a connected state, such that the other terminals(C_OVP1, C_OVP2) of the first and second capacitors C1 and C2 of theover-voltage protector 25 are connected with the ground terminal, and inthis case, the first and second capacitors C1 and C2 of the over-voltageprotector 25 affect the resonator of the resonance signal receiver 24,detuning the resonance frequency. As a result, the signal transmittedfrom the wireless power transmission device 1 cannot be receivedefficiently, which detrimentally affects the power transmission.

The constant-voltage generator 20, the voltage detector 26, thecontroller 28, and the driver 27 may be configured in the form of asingle Integrated Circuit (IC) chip (BUCK-IC).

Referring to FIG. 2, although not shown in FIG. 1, an auxiliaryover-voltage protector 23 including a Zener Diode (ZD) may be furtherincluded between the rectifier 22 and the smoother 21 for additionalcircuit protection. The auxiliary over-voltage protector 23 is notessential, but may be further included to supplement the over-voltageprotection function. The ZD may be set such that for example, abreakdown voltage is 30V to prevent an output voltage VIN of therectifier 22 from exceeding a preset level.

When the over-voltage protector is implemented with only the ZD,over-voltage protection is difficult to achieve in a preparation periodcorresponding to a time required for the ZD to operate, and if theamount of power from the output voltage VIN of the rectifier 22 to aninput voltage BUCK_IN of the constant-voltage generator 20 is large, thenecessary capacity and size of the ZD have to be undesirably increased.Generally, a ZD having a size of about 1608 (16×08 mm) may protect acircuit of about 300 mW. Thus, to protect 1 W in a portable mobiledevice, three or more parts of a size of 1608 or larger have to be used.Since a reception stage of a cellular phone or mobile wireless chargingresonance system has a small mounting space for a product, such thatover-voltage protection should be performed in a small-area region, thereception stage should be protected up to 5 W for a cellular phone andup to 10 W for a tablet phone or a Personal Computer (PC). Thisrequirement is difficult to achieve when the over-voltage protectioncircuit is implemented only with the ZD.

Therefore, in the reception device of the present invention, theover-voltage protection circuit is implemented by usingresonance-detuning capacitors (two 1005 parts).

FIG. 3A illustrates over-voltage protection of the controller 28 of thereception device 2 of FIG. 1. Referring to FIG. 3A, the controller 28 ofthe reception device 2 monitors the input voltage BUCK_IN of theconstant-voltage generator 20 through an output of the voltage detector26 in step 302. Thereafter, in step 304, the controller 28 determineswhether the input voltage BUCK_IN is greater than or equal to a presetover-voltage protection start reference voltage (e.g., 25.7V). If theinput voltage BUCK_IN is not greater than or equal to the presetover-voltage protection start reference voltage, the monitor 28continues the input voltage monitoring operation of step 302. Unless theinput voltage BUCK_IN is greater than or equal to the presetover-voltage protection start reference voltage, the monitor 28 proceedsto step 306 to perform an over-voltage operation.

The over-voltage protection operation of step 306 is performed after areaction time elapses (of about 10 microseconds (μs) or less) after theinput voltage BUCK_IN increases, for example, to 25.7V. The controller28 outputs a control signal to the driver 27 to connect the pins C_OVP1and C_OVP2 of the over-voltage protector 25 to the ground terminal, suchthat the over-voltage level decreases. In this state, the controller 28may transmit a signal indicating that the current state of the receptiondevice 2 is an over-voltage protection operation state, and according tothis signal, the wireless communication unit 29 transmits informationindicating that the reception device 2 is currently in the over-voltageprotection operation state to the transmission device 1.

In step 308, the controller 28 monitors the input voltage BUCK_IN of theconstant-voltage generator 20. In step 310, the controller 28 determineswhether the input voltage BUCK_IN is less than or equal to a presetover-voltage protection-release reference voltage (e.g., 24.8V. If theinput voltage BUCK_IN is not less than or equal to the presetover-voltage protection-release reference voltage, the controller 28continues the input voltage monitoring operation of step 308. Unless theinput voltage BUCK_IN is less than or equal to the preset over-voltageprotection-release reference voltage, the monitor 28 proceeds to step312 to release the over-voltage operation.

As to a procedure for releasing the over-voltage protection operation instep 312, if the over-voltage protection operation is performed in step306 and thus the input voltage BUCK_IN decreases to below 24.8V, anover-voltage recovery operation is performed, such as 700-1000 μs, andthen the controller 28 outputs a control signal to the driver 27 tocontrol the switch structure of the driver 27 to have an open state,such that the pins C_OVP1 and C_OVP2 of the over-voltage protector 25are opened. Thus, the over-voltage protector 25 is deactivated.

After the over-voltage protection operation is released in step 312, thecontroller 28 returns to step 302 to repeat the foregoing process. Ifover-voltage occurrence conditions in the reception device 2 are notsolved, the over-voltage protection operation and the over-voltageprotection-release operation may be repetitively performed.

FIG. 4 illustrates a voltage waveform applied to the constant-voltagegenerator 20 of the reception device 2 of FIG. 2, showing a waveform ofa continuance of the over-voltage protection operation and theover-voltage protection-release operation continue when the over-voltageoccurrence conditions are not solved. Referring to FIG. 4, after aninitial wireless power reception operation, the internal 3V Low DropOut(LDO) of the constant-voltage generator 20 operates when the outputvoltage VIN of the rectifier 22 is about 4V. Then the waveform of theoutput voltage VIN increases and at 4V, the waveform becomes level forabout 250 μS. Thereafter, the output voltage VIN continuously increases.

The 3V LDO supplies power (3V, 40 mA max) to the external controller 28(e.g., the MCU). A boot-up time that can be controlled by a GeneralPurpose Input/Output (GPIO), which is the external controller 28, is 7.2mS. The constant-voltage generator 20 operates, e.g., at the inputvoltage BUCK_IN of 5.5V, and outputs a constant voltage such as 5V.

Thereafter, an over-voltage protection operation starts after a responsetime at the output voltage VIN of, for example, 25.7V. The pins C_OVP1and C_OVP2 of the over-voltage protector 25 are connected to the groundterminal by means of the switch structure of the driver 27. Then, asignal OVP which indicates the over-voltage protection operation stateis activated by the controller 28 (signal OVP L=>H: over-voltageprotection operation state).

At the output voltage VIN of 24.8V or less, for example, theover-voltage protection operation is released after an over-voltagerecovery time. In this state, the pins C_OVP1 and C_OVP2 are opened andthe signal OVP is deactivated by the controller 28 (signal OVP H=>L:normal state).

As the over-voltage protection operation and the over-voltageprotection-release operation are continued when the over-voltageoccurrence conditions are not solved in the reception device 2, theoutput voltage VIN periodically shows a waveform which rises over theover-voltage protection start reference voltage (e.g., 25.7V) and fallsbelow the over-voltage protection-release reference voltage (e.g.,24.8V).

FIGS. 5A through 5C illustrate voltage waveforms applied to theconstant-voltage generator 20 for respective set capacities of therespective detuning capacitors C1 and C2 included in the over-voltageprotector 25 of the reception device 2 of FIG. 2, in which a periodicwaveform of the input voltage BUCK_IN applied to the constant-voltagegenerator 20 when the over-voltage occurrence conditions are not solvedis shown.

FIGS. 5A through 5C illustrate the waveforms of the input voltageBUCK_IN when the capacities of the detuning first and second capacitorsC1 and C2 of the over-voltage protector 25 are 2.2 nanoFarads (nF), 4.7nF, and 22 nF, respectively. It can be seen that when the capacities ofthe detuning capacitors are different (as will be described below, forthe capacity of 2.2 nF or more), the respective waveforms showperiodicity without any significant difference therebetween.

However, for the capacity of 2.2 nF or less, the over-voltage protectionoperation is not performed effectively, as will be described below indetail with reference to FIG. 6.

FIG. 6 illustrates a rate of power transferred from the transmissiondevice 1 to the reception device 2 with respect to a set capacity ofeach detuning capacitor included in the over-voltage protector 25 of thetransmission device 2 of FIG. 2, and FIGS. 7A through 7F illustrate arate of power transferred from the transmission device 1 to thereception device 2 with respect to a set capacity of each detuningcapacitor included in the over-voltage protector 25 of the receptiondevice 2 of FIG. 2. FIG. 7A illustrates when the detuning capacitors areopen (or a normal state when there is no capacitor), and FIGS. 7Bthrough 7F illustrate when the capacities of the detuning capacitors are2.2 nF, 5.0 nF, 7.0 nF, 10.0 nF, and 22.0 nF, respectively.

Referring to FIGS. 6 and 7A through 7F, once the pins C_OVP1 and C_OVP2for the detuning capacitors are opened, a rate of power transferred fromthe transmission device (resonator) to the reception device (resonator),S21, is about 80-90%, indicating that power transmission from thetransmission device to the reception device has been successfullyperformed.

As shown in FIG. 7B, if the capacities of the detuning capacitors are2.2 nF, upon connection of the pins C_OVP1 and C_OVP2 to the groundterminal, about 60% of the transmission power is transferred to thereception device. Likewise, as shown in FIGS. 7C and 7F, when thecapacities of the detuning capacitors are 5.0 nF, 7.0 nF, 10.0 nF, and22.0 nF, respectively, about 38.5%, 26.7%, 13.2%, and 4.1% of thetransmission power are transferred, respectively. In FIG. 7F, for thecapacity of 22 nF, S21 is 4.1%, such that little or no powertransmission is performed.

In the above description, if the capacity of the detuning capacitor istoo small (e.g., 2 nF or less), S21 is 61%, such that even if theover-voltage protection operation is performed, over-voltage protectionmay not be achieved and thus the voltage may continuously increase. Thisis because the detuning effect is not large even if the over-voltageprotection operation is performed and thus the pins C_OVP1 and C_OVP2for the detuning capacitors are connected with the ground terminal. Inthis case, the output voltage VIN continuously increases, which damagesinternal components of the reception device. When the detuning capacitorof 2.2 nF is used in which S21 of the power transferred from thetransmission device to the reception device is experimentally reduced by30%, S21 is about 60%.

Thus, in the present invention, the capacities of the detuningcapacitors are set to a value in which ΔS21 is 30% or more, as given inEquation (1) by:

ΔS21=(S21)−(S21 in over-voltage protection state)   (1)

It can be seen that S21, which is a rate of the power transmitted fromthe transmission device to the reception device, after execution of theover-voltage protection operation is 30% reduced from S21 beforeexecution of the over-voltage protection operation.

In view of a Voltage Standing Wave Ratio (VSWR, reflection coefficient),transmission of power at 60% or less indicates that a reflectioncoefficient is greater than 4. That is, when the over-voltage protectionoperation is executed, VSWR≧4.

In view of a Q value, a change of the Q value is more than 0.1. That is,Q may be expressed in Equation (2) as follows:

Q=(Δf/13.56)*1.5 (Δf indicates a frequency variation)   (2)

Thus, for example, for Δf=1 MHz, Q=0.11. As such, for the Q value of 0.1or more, the frequency may be regarded as detuned.

As described above, the over-voltage protection operation is performedby detuning the resonance frequency at the reception device 2 using thedetuning capacitors. The reception device has to continuously repeat theover-voltage protection operation when the over-voltage occurrenceconditions are not solved, unless other measures are taken.

Moreover, the controller 28 of the reception device 2 may be configuredto recognize the over-voltage state and transmit a message requestingthe transmission device 1 to solve the over-voltage problem to thetransmission device 1 through the wireless communication unit 29. Untilover-voltage protection is performed, however, this process is verytime-consuming. Therefore, it may be preferable that the transmissiondevice 1 directly determines and then cancels the over-voltage state. Inthe present invention, therefore, the transmission device 1 instantlydetermines the over-voltage state of the reception device 2 and reducesthe power transmitted from the transmission device 1, thereby protectingthe reception device 1.

FIG. 3B illustrates over-voltage protection of the controller 18 of thetransmission device 1 of FIG. 1. Referring to FIG. 3B, the controller 18monitors a resonance-stage voltage of the resonance signal generator 14through an output of the voltage/current detector 16 in step 320. As thereception device 2 periodically executes the over-voltage protectionoperation and release operation as mentioned previously, the waveformsas shown in FIG. 4 or FIGS. 5A through 5C are generated. Likewise, (apeak value of) the voltage detected in the resonance stage of thetransmission device 1 also exhibits a similar waveform. That is, even ifthe transmission device 1 transmits a constant output through theamplifier 12, the voltage of the resonator of the resonance signalgenerator 14 changes according to the frequency resonance.

In step 322, the controller 18 of the transmission device 1 determineswhether rise and fall are repeated at particular intervals, such as 500μS-2 mS when the resonance-stage voltage is sampled and a value thereofis larger than a preset over-voltage reference voltage (e.g., 15V)during a period. If corresponding determination conditions are notsatisfied, the controller 18 returns to step 320 to continue monitoringthe resonance-stage voltage, whereas if the determination conditions aresatisfied, the controller 18 proceeds to step 324.

In step 324, the controller 18 of the transmission device 1 regards thatthe reception device 2 is currently in the over-voltage state, and thuscontrols the output of the transmission device 1 to be reduced by avalue, such as 30% or higher, during a period. The controller 18performs a control operation such that the output of the amplifier 12 isreduced. Herein, decreasing the output by 30% or more is an importantfactor because if the output is decreased by 30% or less, in spite ofexecution of the over-voltage protection operation, over-voltageprotection is not achieved in the reception device 2 such that thevoltage may continuously increase.

After execution of the operation of step 324, the controller 18 returnsto step 320 to repeat the foregoing operation.

By executing the foregoing operation, even if the reception device 2does not inform the transmission device 1 of the over-voltage situation,the transmission device 1 may automatically sense the over-voltagesituation of the reception device 2 and reduce the transmission power,thereby handling the over-voltage situation. By reducing thetransmission power, the over-voltage situation in the reception device 2is released.

In addition, by monitoring the magnitude of the voltage transmitted fromthe transmission device 1, the transmission power for over-voltageprotection is controlled, which conserves the time taken for thereception device 2 to receive a signal indicating the over-voltagesituation, thereby rapidly protecting a circuit from the over-voltagestate.

As such, the over-voltage protection scheme for the resonant wirelesspower transmission device according to the present invention may berealized. Embodiments of the present invention have been described inthe foregoing description, but other embodiments or modifications orchanges thereto may be made.

For example, while the reception device 2 corresponding to thetransmission device 1 according to the present invention adopts aconfiguration using a resonance frequency detuning scheme in theforegoing description, the voltage waveform of the resonance stagesensed by the transmission device 1 may experience periodicity when thereception device 2 repeats the over-voltage protection operation andrelease operation even if the reception device 2 adopts an over-voltageprotection circuit having other configurations. It can also beunderstood that the transmission device 1 according to the presentinvention effectively handles the over-voltage situation by performingthe disclosed over-voltage protection operation.

In addition, while the transmission power is decreased by 30% forover-voltage protection in the transmission device 1 in the foregoingdescription, the transmission device 1 may shut down the transmissionpower for over-voltage protection.

In the foregoing description, the detuning capacitors in the receptiondevice 2 are selectively connected with the ground terminal by thedriver when they are connected to the resonance stage, but they may alsobe selectively connected with the resonance stage by the driver whenbeing connected with the ground terminal.

The controller 28 of the reception device 2 may provide informationregarding execution of the over-voltage protection operation to aportable terminal to which the reception device 2 is applied, such thatthe information is displayed on a display device of the portableterminal or may be output as an alarming sound through a speakerprovided in the portable terminal.

In the reception device 2, the controller 28 may further decrease theover-voltage protection-release reference voltage or may transmit amessage requesting stop of power transmission to the transmission device1, if the over-voltage protection operation and release operation arecontinuously repeated at intervals.

As is apparent from the foregoing description, the over-voltageprotection scheme for the resonant wireless power transmission deviceaccording to the present invention solves a size increase problem whileoffering rapid handling and high efficiency.

While embodiments of the present invention has been described, it willbe obvious to those of ordinary skill in the art that variousmodifications can be made without departing from the scope of thepresent invention.

1. A wireless power transmission device comprising: a resonance signalgenerator configured to transmit wireless power to a wireless powerreception device; and a controller configured to adjust the wirelesspower transmitted to the wireless power reception device, when apredetermined condition caused by an over-voltage protection operationat the wireless power reception device is detected.
 2. The wirelesspower transmission device of claim 1, wherein the predeterminedcondition is a voltage variation at the resonance signal generator. 3.The wireless power transmission device of claim 2, wherein the voltagevariation at the resonance signal generator occurs by detuning aresonant frequency of the wireless power reception device.
 4. Thewireless power transmission device of claim 2, wherein the predeterminedcondition is that the voltage repetitively increases and decreases withperiodicity.
 5. The wireless power transmission device of claim 4,wherein the periodicity of the voltage variation is 500 microseconds(μS)-2 milliseconds (mS).
 6. The wireless power transmission device ofclaim 2, if the controller detects the voltage variation at theresonance signal generator, the controller decreases an output of thewireless power transmission device.
 7. The wireless power transmissiondevice of claim 6, further comprising: an amplifier for amplifyinginputted power and outputting the amplified power to the resonancesignal generator, wherein the controller controls the amplifier so thatthe output of the wireless power transmission device is decreased by atleast 30%.
 8. The wireless power transmission device of claim 6, furthercomprising: an amplifier for amplifying inputted power and outputtingthe amplified power to the resonance signal generator, wherein thecontroller controls the amplifier so that the output of the wirelesspower transmission device is shut down during a preset period.
 9. Thewireless power transmission device of claim 1, wherein the wirelesspower reception device changes a resonant frequency as the over-voltageprotection operation.
 10. A method for controlling a wireless powertransmission device comprising: transmitting wireless power to awireless power reception device; and adjusting the wireless powertransmitted to the wireless power reception device, when a predeterminedcondition caused by an over-voltage protection operation at the wirelesspower reception device is detected.
 11. The method of claim 10, whereinthe predetermined condition is a voltage variation at a resonance signalgenerator of the wireless power transmission device.
 12. The method ofclaim 11, wherein the voltage variation at the resonance signalgenerator occurs by detuning a resonant frequency of the wireless powerreception device.
 13. The method of claim 11, wherein the predeterminedcondition is that the voltage repetitively increases and decreases withperiodicity.
 14. The method of claim 13, wherein the periodicity of thevoltage variation is 500 microseconds (μS)-2 milliseconds (mS).
 15. Themethod of claim 11, further comprising: decreasing an output of thewireless power transmission device, if the voltage variation at theresonance signal generator is detected.
 16. The method of claim 15,wherein decreasing the output of the wireless power transmission devicecomprises decreasing the output of the wireless power transmissiondevice by at least 30%.
 17. The method of claim 15, wherein decreasingthe output of the wireless power transmission device comprises shuttingdown the output of the wireless power transmission device during apreset period.
 18. The method of claim 10, wherein the wireless powerreception device changes a resonant frequency as the over-voltageprotection operation.